Arc head mechanism for searchlights



Feb. 14, 1939. w. H. JACOBI ET AL ARC HEAD MECHANISM FOR SEARCHLIGHTS Filed June 19, 1937 iso Patented Feb. 14, 1939 UNITED STATES PATENT CFFICE ARC HEAD MECHANISM FOR SEARCHLIGHTS William H. Jacobi, Wilkinsburg, Pa., and Irvine A. Yost, Lakewood, Ohio, assignors to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 19, 1937, Serial No. 149,156

Which shall be so shaped as to prevent the arc flame from striking the arc shield.

A iurther object of the invention is to provide mechanism comprising a plurality of parts, each of which shall function to dissipate a portion 5 of the heat from the arc tip of an electrode of a high intensity arc searchlight, and Which shall be so designed as to distribute the burden of dissipation between these parts so as to prevent overheating of any one part.

These and other objects and advantages of our invention will be apparent from the following description taken in connection With the accompanying drawing, in which:

Figure l is a side elevation View of the are head 15 of an arc searchlight with parts of the mechanism shown in outline, parts in section, and some parts Which are not essential to an understanding of this invention; and,

Fig. 2 is a plan view of the positive electrode 20 holder and associated mechanism of Fig. 1 as viewed from the position indicated by the line 1i-II of Fig. 1.

In practicing our invention, a frame is provided or supporting a mechanism which operates to feed an electrode to an arc as the electrode is consumed in the arc and to rotate the electrode to insure uniform burning of the electrode and to prevent cracking and chipping of the electrode tip due to the intense heat of the arc. Also mounted upon this frame is a metal sleeve through Which the electrode is fed by the feeding and rotating mechanism. Current for operating the arc is conducted to the electrode by brushes which extend through slots in the side of the sleeve and bear upon the electrode.

An arc shield is mounted upon the sleeve to help dissipate the heat from the arc and to shield the operating mechanism from the heat radiated from the arc. This shield is heatinsulated from the sleeve by mica Washers Which form part of the means for mounting the shield upon the sleeve. The shield has an indentation in its upper side to prevent the shield being damaged by Contact with the upwardly extending are flame. The shield is further protected from damage by heat by spacing the shield supporting sleeve from the electrode so that a layer of gas may he formed and. provide heat insulation be- 8 Claims.

Our invention relates, generally, to arc searchlights, and, more particularly, to the construction of an arc head mechanism for high intensity arc searchlights.

In the operation of electric arc searchlghts it is common practice to provide a mechanism for rotating the positive electrode to insure even burning of the electrode and for feeding the electrode to the arc to compensate for the consumption of the electrode in the are to thereby maintain the arcing tip in substantially the saine position at all times. Such mechanisms are usually positioned baci: ci the arc tip and in this position are exposed to the heat radiated and conducted from the arc. In arcs oi very high intensity, the heating ci the electrode rotating and feeding mechanism may be sufcient to cause warping of this mechanism or cause the mechanism to jam and fail to operate.

The heat generated in the arc must be dissipated to prevent injury to the operating mechanisms. Heretoore, arc shields have been provided to shield the mechanism from the arc. Heat radiators have also been used as Well as Ventilating means to circulate air through the searchlight,

The devices used heretofore have proved inadequate when used with arcs of extremely high intensity such as are used with 60 inch reflectors and which operate at currents of from 1.50 to 250 amperes and it has been necessary to devise additional and improved protecting means for the electrode operating mechanism.

The object of this invention is to provide a device which shall operate to prevent damage to the electrode operating mechanism or" a high intensity arc searchlight due to heat conducted and radiated 'from the arc.

Another object of the invention is to provide a device which shall operate to minimize the heat conduction from the arc shield to the electrode operating mechanism of a high intensity arc searchlight.

A further object of the invention is to provide a device which shall function to minimize heat conduction from the electrode to the arc shield of a high intensity are searchlight.

Another object oi the invention is to provide a mechanism which shall function to shield the electrode operating mechanism from heat radiatween 'GheSS elements. 50 tion from the arc shieid shall also function The brush Supporting sleeve is also spaced, as a radiator to dissipate heat conducted from from the electrode to provide heat insulation as the electrode tip by the electrode. just described. The brush supporting sleeve is Another object of the invention is to provide provided with radiating fins to help dissipate an are shield for a high intensity arc searchlight the heat from the electrode and arc. An auX- Vface to act as radiators to iliary radiating device is provided to help lower the temperature of the electrode to prevent too great heating of the electrode actuating mechanism. This auxiliary radiating means also serves as a shield to protect the electrode actuating mechanism from the heat radiated from the arc shield.

Referring to the drawing and to Figure 1 in particular, a frame including members I, 2, 3

and I3 (see Fig. 2) is provided for supporting'V the electrode positioning and actuating mechalllSIllS. toward the arc by a mechanism 4 which is not shown in detail, since its detailed operation is not an essential part of this invention. This mechanism may be any of the common mechanisms for performing the function of rotating and feeding an electrode and may be such a mechanism as is disclosed in the copending application of I. A. Yost, et al. filed October 3, 1935, Serial No. 43,372 now Patent No. 2,117,888, issued May 17, i938.

A brushholder 5 is also mounted upon this framework and has brushes 6 extending through slots in the sides of the brushholder and bearing upon the positive electrode. This brushholder is in the form of a sleeve and has fins 'I on its surdissipate the heat from the electrode.

Auxiliary radiators 8 are provided and these radiators are mounted upon the brushholder 5 by screws 9. These radiator members 8 are spaced by metallic washers I to provide ventilating space between the members and to provide heat conducting elements between the members and from the brushholder to the members. These radiator members are in the form of metallic disks and are made of such dimensions as to shield a large portion of the operating mechanism 4 from heat radiated from the member II.

The member II is an arc shield which absorbs and radiates heat from the arc and the electrode and is of such size as to prevent heat radiation `from the arc to the operating mechanism 4. Arc shield I I is secured to frame member I3 by means of bolts I2 (see Fig. 2). Arc shield II is insulated from brushholder 5 by mica washer I4 and from frame member I3 by mica washer I5 to prevent conduction of heat from the arc shield to the frame and to the brushholder. 'Ihis insulation is necessary for the reason that the arc shield, being very near to the arc and to the hottest part of the electrode, becomes very hot in the operation of thearc and it is necessary that this great heat be insulated from metallic members which might conduct the heat to the operating mechanism 4 and thus damage it or cause it to jam.

The arc flame I6 which is formed when an arc is struck between negative and positive electrodes Il and i3 assumes a form which is approximately that shown in Fig. 1. It will be seen that this flame extends toward the arc shield,rand it is necessary that the arc shield be so shaped as to prevent the flame from actually contacting the arc shield. This is done by forming the portion I8 of the arc shield in such a manner as to allow the name to extend upward without striking the portion of the shield as shown in the drawing.

As a means for further providing heat insulation between the positive electrode I8 and therarc shield, the 'sleeve 28 through which electrode I 8 Y extends and'which Yprovides a support for the arc shieldris so dimensioned as to space itsrwalls substantially from the electrode I8. This provides av space which lls with gases which are given 01T The positive electrode is rotated and fedV by the highly heated electrode and which serve as a heat insulating layer between the electrode and the arc sleeve. A similar insulating space is provided between the electrode I8 and the brushholder 5 for the same purpose. The filling of these spaces with gases also excludes the air from contact with the electrodes at these points and so prevents burning of the .electrodes beyond the arc tip.

In the operation of the device, while the arc is burning, the arc shield II absorbs heat from the arc and from the heated end of the electrode and dissipates it from its surface. This provides a medium for reducing the temperature of the elecrode in the proximity of the arc shield. The portion of the electrode I8 which extends through brushholder 5 is less hot than that portion which extends through the arc shield sleeve 20, but itis still necessary to dissipate considerable heat from this portion of the electrode to prevent conduction of too great an amount of heat to the electrode actuating mechanism 4. The dissipation of the heat from this area is accomplishedby the ribs l on the brushholder 5 and the radiating members 8 which constitute the auxiliary radiator and which are secured to the brushholder 5 between the brushholder 5 and the actuating mechanism 4.

The auxiliary radiators 8 are positioned between the brushholder 5 and the actuating mecha- Ynism 4 to function as a shield to prevent heat radiation from the arc shield II and from the brushholder 5 to the actuating mechanism 4. It will be seen that these radiators thus perform the dual function of radiating and shielding.

The mechanism 25 for feeding the negative electrode i'I to the arc is not so complicated as actuating mechanism 4 and is so situated with respect to the arc flame as to require less heat protection Vfrom the flame. Means are provided, however, for preventing too great radiation and conduction of heat to this mechanism. These means comprise fins 2! on the brushholder for the negative electrode and auxiliary radiators 22 which have the same construction as radiators 8, a heat insulating washer 23 and metal washers 24.

It will be seen that each of these heatinsulating and radiating elements helps to dissipate a carries its own share of the burden of dissipating this heat so that the actuating mechanism for the positive and negative electrodes will not be heated to such an extent as to cause it to fail to function.

In compliance with the requirements of the patent statutes, we have shown and described herein a preferred embodiment of our invention. It is understood, however, that the inventien is not limited to the precise construction shown and described but is capable of modification by one skilled in the art, the embodiments herein shown being merely illustrative of the principles of our'invention.

We claim as our invention:

1. In an electrode positioning and actuating mechanism for a high intensity arc searchlight, a sleeve member having heat radiating fins ther-@ on and having an opening longitudinally therethrough through which the electrode extends. an arc shield through which the electrode extends mounted forwardly of the end of the sleeve member and insulated therefrom by heat insulating material, an electrode actuating mechanism mounted substantially coaxial of and adjacent thev other end of the sleeve member, and auxiliary radiating means mounted on the sleeve member between said sleeve member and said actuating mechanism, said auxiliary radiating means being so shaped as to shield said actuating means from heat radiation from said arc shield, the dimensions of said sleeve member and said arc shield being such as to provide substantial spacing between the electrode and the walls of the electrode receiving openings oi said shield and sleeve member, said arc shield being formed with a depression in the upper side of its surface which is adjacent the arcing tip of the electrode to prevent the upwardly extending flame from the arc from contacting the arc shield.

2. In an electrode positioning and actuating mechanism for a high intensity arc searchlight, an arc shield comprising a sleeve member surrounding the electrode, a iiange member surrounding and extending from the sleeve member substantially normal thereto, said flange portion having a portion thereof displaced away from the arc-tip side so that the flame from the arc may not contact the iiange portion.

3. In an arc shield for a high intensity arc searchlight, an imperforate sleeve constituting the supporting hub for said shield, said sleeve having such dimensions as to substantially space the inner walls of the sleeve from the electrode as the electrode exten-ds through the sleeve so as to provide a gas chamber between said sleeve and the electrode.

4. In an are searchlight, an electrode, an arc shield having a passage through which said electrode extends, a sleeve member through which said electrode extends having heat radiating members thereon, the dimensions oi said passage and of the inside of said sleeve being such as to provide substantial spacing between said electrode and said shield and sleeve to thus provide a gas chamber therebetween, and means for securing said shield to said sleeve comprising members of heat insulating material.

5. In an arc searchlight, an electrode, an arc shield having a passage through which said electrode extends, a sleeve member through which said electrode extends having slots through which brushes for conducting electric current to said electrode extend and having radiating fins thereon, the sleeve and said passage being coaxial and of such dimensions as to provide a substantial gas space between said electrode and said shield and sleeve, and means for securing said shield to said sleeve comprising members of heat insulating material therebetween.

6. In an arcing device, an electrode, means for conducting electric current to said electrode as the electrode is fed to the arc comprising brush means and a sleeve through which said brush means extends to contact the electrode as it passes through the sleeve, said sleeve having heat radiating iins thereon, and an auxiliary radiating means secured to said sleeve comprising plates secured in heat conducting relation with and coaxial of said sleeve.

7. In an arc searchlight, an electrode, means for actuating said electrode, means for conducting electric current to said electrode as the electrode is actuated comprising brush means and a sleeve through which said brush means extends to contact the electrode as it passes through the sleeve, said sleeve having radiating fins thereon and an auxiliary radiating means secured to said sleeve between said sleeve and said actuating means comprising heat conducting plates secured in heat conducting relation with and coaxial oi said sleeve, said sleeve being mounted between the arcing tip oi said electrode and said actuating means.

8. In an arc searchlight, an electrode, a mechanism for actuating said electrode, an arc shield disposed adjacent the arcing tip of said electrode and between the arcing tip and said electrode actuating mechanism, and a spaced auxiliary heat radiating means disposed between said shield and said actuating mechanism for dissipating heat conducted from said are shield and said electrode toward said actuating mechanism, said radiating means comprising plates of heat conducting material disposed coaxially of said electrode and extending substantially radially therefrom such a distance as to shield said actuating mechanism from heat radiating from said arc shield.

WILLIAM H. JACOBI. IRVINE A. YOST. 

